Write Head Having Recessed Magnetic Material In Gap Region

ABSTRACT

As track densities increase, it becomes increasingly important, while writing in a given track, not to inadvertently write data in adjoining tracks. This problem has been overcome by limiting the width of material in the ABS plane to what it is at the write gap. The part of the lower pole that is wider than this is recessed back away from the ABS, thereby greatly reducing its magnetic influence on adjacent tracks. Four different embodiments of write heads that incorporate this notion are described together with a description of a general process for their manufacture.

This is a divisional application of U.S. patent application Ser. No.10/706,381 filed on Nov. 12, 2003, which is herein incorporated byreference in its entirety, and assigned to a common assignee.

FIELD OF THE INVENTION

The invention relates to the general field of magnetic write heads withparticular reference to eliminating neighboring track erasure.

BACKGROUND OF THE INVENTION

A typical write head structure for a magnetic disk system isschematically illustrated in FIG. 1. Its principal parts are lower pole12 and upper pole 11 (commonly referred to as P1 and P2, respectively.These are magnetically connected at one end and separated by a smallnon-magnetic layer 13 (the write gap) at the other end. The track widthwill be defined by the P2 width at the gap. P1 may be notched through aself aligned process, known as partial pole trim (PPT), to better definethe written transitions. Coil 14 is located in the space enclosed by P1and P2 and is the source of the magnetic field that is focused by thetwo pole pieces. All seen in the figure is a magnetic shield layer 16which is electrically isolated from the lower pole by dielectric layer15.

FIG. 2 shows a variation on the basic design seen in FIG. 1. In thiscase a secondary upper pole 21 is ‘stitched’ in between 11 (P2) and gap13. This is for ease of fabrication so that the track width definitioncan be done on relatively flatter topography. An additional feature, notpresent in the design of FIG. 1, is shallow trench 22 which is etchedinto lower pole 12. Since trench 22 has sloping sides, the depth towhich it is etched can be used to fine tune the length of lower pole 12that is part of the write gap 13. This is usually referred to as thethroat. This allows for a further concentration of the available fluxwithin the write gap. In the stitched pole design, the track width isdefining part of pole 21 as well as the back gap connection 23 which arefabricated immediately following the deposition of write gap 13.

FIG. 3 is an isometric view of part of FIG. 1 or FIG. 2 as seen whenlooking up from the magnetic track at the air bearing surface thatpasses over it (so-called ABS view). It is important to note that thesurfaces of the upper pole (11 in FIG. 1 or 21 in FIG. 2), the gap 13,and the lower pole 12, are all coplanar. One consequence of this, thestandard structure in use today, is the unintended erasure of adjacenttracks on the disk as narrower tracks and higher track densities aredeveloped. Most improvements that have been proposed, such as increasedPPT depth, smooth P 1 topography, and narrower gap all come with eitherprocess challenges or reduced on track writeablity performance.

As track densities increase, the read head extracts the recordedinformation from an ever decreasing narrow track. It becomesincreasingly important not to affect the integrity of this narrow trackof data. In the structure shown in FIG. 3, P2 has magnetic materialconfined to the written track. P1. however, still includes material thatextends outside the track width (TVV) defining region. This may lead tounintended writing on an adjacent track and may therefore affect thedata integrity of the system.

A routine search of the prior art was performed with the followingreferences of interest being found:

U.S. Pat. No. 6,353,511 B1 (Shi et al.) shows a process for a improvedWrite head. U.S. Pat. No. 5,878,481 (Feng et al.) shows a pole trimmingprocess for a write head. U.S. Pat. No. 5,843,521 (Ju et al.) and U.S.Pat. No. 5,802,700 (Chen et al.) are related patents. U.S. Pat. No.5,652,687 (Chen et al.) shows a planarized write head process.

SUMMARY OF THE INVENTION

It has been an object of at least one embodiment of the disclosedstructure to provide a magnetic write head that does not writeunintentionally onto data tracks located on either side of the trackthat is being written.

Another object of at least one embodiment of the disclosed structure hasbeen that this be accomplished without a reduction in write fieldstrength or track density.

Still another object of at least one embodiment of the disclosedstructure has been to provide a process for the manufacture said writehead.

A further object of at least one embodiment of the disclosed structurehas been that said process not require significant modification ofexisting processes for the manufacture of write heads.

These objects have been achieved by limiting the width of material inthe ABS plane to what it is at the write gap. The part of the lower polethat is wider than this is recessed away from the ABS, thereby greatlyreducing its magnetic influence on adjacent tracks. Four differentembodiments of write heads that incorporate this notion are describedtogether with a description of a general process for their manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a basic read head design.

FIG. 2 shows the basic design of FIG. 1 modified by use of a stitchedupper pole.

FIG. 3 is the ABS view of FIGS. 1 and 2 in isometric projection.

FIG. 4 shows the structure of FIG. 1 modified according to the teachingsof the disclosed structure.

FIG. 5 shows the structure of FIG. 2 modified according to the teachingsof the disclosed structure.

FIG. 6 illustrates a third embodiment of the disclosed structure.

FIG. 7 is an isometric view of a portion of a fourth embodiment.

FIGS. 8-12 illustrate successive steps in the manufacture of thedisclosed structure.

FIG. 13 is a plan view of the disclosed structure.

FIG. 14 is an isometric view of part of a fourth embodiment of thedisclosed structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The key novel feature of the disclosed structure is the restriction ofthe width of P1 to TW for a distance such that there is no P1 wider thanthe track width at the ABS.

This is achieved by causing P1 beyond this distance to be recessed awayfrom the ABS, thereby greatly reducing its magnetic influence on theadjacent tracks. Thus, the amount of P1 at the ABS should exceed theamount of P1 that is recessed

1^(st) Embodiment

Referring now to FIG. 4, we show there a structure that is similar tothe one shown in FIG. 1, but modified in accordance with the teachingsof the disclosed structure. As before, upper pole 11 and lower pole 12enclose, between them, field coil 14. The key novel feature is ledge 41of magnetic (high permeability) material that extends outwards away fromthe main body of lower pole 12. The outer edge of ledge 41 has the samewidth as, and is in alignment with, the outer edge of top pole 11 sothat write gap 13 lies between them and said widths define the trackwidth TW. As a result, most of bottom pole 12 is set back some distancefrom the ABS and so has relatively little magnetic interaction with thedisk surface. FIG. 7 is an isometric view that illustrates the spatialrelationships between top pole 11 and bottom poles 41 and 12.

For purposes of simplification, FIG. 4 has been drawn as though ledge 41is a cantilever. In actuality, a layer of insulation is present below 41to support it. Details of this support layer are provided later, in thesection where we describe the process for manufacturing this structure.

2^(nd) Embodiment

FIG. 5 shows a structure similar that seen in FIG. 2. As before, thereis a general similarity to the first embodiment illustrated in FIG. 4with the addition of stitched secondary top pole 21 and shallow trench22. The key departure is the addition to the structure of ledge 51,which analogous to ledge 41 of the first embodiment, and serves the samepurpose. FIG. 7 is an isometric view that illustrates the spatialrelationships between top pole 21 and bottom poles 51 and 12 while FIG.13 is a plan view of this structure.

3^(rd) Embodiment

This variation of the basic structure is sometimes preferred becausecertain parts, such as pole 11, are easier to manufacture. By going to asomewhat thicker inter-pole connector 23 and using a single turn forfield coil 23, top pole 11 can be flat rather than humped, as in theprevious two embodiments. The bottom pole in this case is composed oftwo layers, 62 and 12, which, in prior art versions of this variant (notshown), would extend from bottom pole 12 all the way to write gap 13.

As seen in FIG. 6, in the disclosed structure the secondary bottom poleis in two parts 62 and 63. Part 62 extends upwards from bottom pole 12but not all the way to write gap 13. This leaves room for second part 63which, in addition to extending the rest of the way up to the write gap,also extends laterally away from part 62 so as to be aligned with theABS end of top pole 11. As a result, the lower part of the secondarybottom pole and all of the main bottom pole 12 are set back from theABS, thereby reducing their magnetic interaction with the write track.

4^(th) Embodiment

This embodiment, illustrated in FIG. 14, entails still furthermodification of the three embodiments just discussed. In all threecases, there is no recessing of the secondary lower poles, recessingbeing delayed so that portion 12 a of the primary lower pole alsoremains coplanar with the ABS. The remainder 12 b of the primary lowerpole is recessed as in the previous embodiments. This embodiment isunsuitable for extremely high track densities (greater than about125,000 tracks per inch) but for lesser densities its advantage ismanufacturability; the thickness and height of 12 a (the non-recessedpart of P1) and the depth of the partial pole trim (41, 51, 62) do notneed to be the same.

Manufacturing Process

Referring now to FIG. 8, the process of manufacturing the disclosedstructure begins with the provision of substrate 15 on which isdeposited, and then patterned, layer 12 of a high magnetic permeabilitymaterial to form the primary lower pole. Next, as seen in FIG. 9, layerof insulating material 91 is deposited on substrate 15 as well as onprimary lower pole 12, making sure that its thickness exceeds that of12.

The structure is then planarized until all insulating material has beenremoved from over the primary lower pole so that the remaininginsulation abuts, and extends away from, the primary pole. This isillustrated in FIG. 10. Second layer 110 of high magnetic permeabilitymaterial is next deposited and patterned to form a secondary lower polethat covers primary pole 12 and extends over insulating layer 91 on oneside so as to form ledge 112. Optionally, an additional layer 114 ofinsulation may be introduced (in the same way as just described for 91)to fill in the part above 91 that is not covered by 110. Since 110 isrelatively thin, this step may be omitted without significantconsequence.

In the case of the second embodiment (FIG. 5), shallow trench 22 isformed at this time. For all embodiments, completion of the structurenow proceeds along routine lines—field coil 14 is formed over, andinsulated from, the lower poles following which the upper magnetic pole11 is formed to overlie it. At one end the two poles are in magneticcontact with one another while at the other end they are by layer ofnon-magnetic material 13 to form the write gap whose width serves todefine the track width TIN. Finally, the ABS end of the structure isplanarized as far as plane 115, thereby determining how far ledge 112extends out away from the main body of the lower pole.

1. A magnetic write head, comprising: on a substrate, a flat primarylower magnetic pole having a first length and first and second ends; ata separation distance over said lower magnetic pole, a flat uppermagnetic pole having a second length that is greater then said firstlength whereby said upper pole has an end, that has a width, thatprojects beyond said lower pole only at said first end; said upper polebeing magnetically connected to said lower pole at said second end;between said upper and lower poles, a field coil that is insulated fromboth said poles; a secondary lower pole having first and second parts;said first part extending upwards from said primary lower pole's firstend to a first height; said second part extending laterally from saidfirst part so as to be in alignment with said upper pole end; saidsecond part also extending upwards to a second height above said lowerpole that is greater than said first height; and said second part beingseparated from said upper pole by a layer of non-magnetic material,whereby it forms a write gap, said second pole having a width, at thewrite gap, equal to said upper pole width, whereby it defines a trackwidth.
 2. The magnetic write head described in claim 1 wherein the firstlength of said primary magnetic pole is between about 5 and 25 microns.3. The magnetic write head described in claim 1 wherein the separationdistance over said lower magnetic pole is between about 0.05 and 0.2microns.
 4. The magnetic write head described in claim 1 wherein thewidth of said upper pole end is between about 1.5 and 3 times said trackwidth.
 5. The magnetic write head described in claim 1 wherein saidfirst height is between about 0.1 and 0.5 microns.
 6. The magnetic writehead described in claim 1 wherein said second height is between about0.1 and 1 microns.